In the related art, there is a line lighting display device in which light is incident to an edge surface of a light guide body, and the light propagates inside the light guide body through total reflection, and is emitted from an upper surface of the light guide body by prisms or dots disposed on a lower surface of the light guide body. Regarding a structure of prisms or dots formed on a light guide body lower surface, there is a structure in which a section thereof has a simple triangular shape, or a structure in which a recessed and smoothly curved surface is disposed between triangular prisms. For example, there is a light guide body having a shape disclosed in PTL 1 as illustrated in FIG. 24.
In FIG. 24, the reference numeral 6 indicates a light guide body, the reference numeral 8 indicates a prism whose section has a triangular shape, and the reference numeral 9 indicates a recessed and smoothly curved surface disposed between the prisms. If light propagating through light guide body 6 is incident to prisms 8, the light is emitted to the outside from light guide body 6, and if the light is incident to curved surfaces 9 between the prisms, the light is diffused. Disposed curved surface 9 diffuses light propagating through light guide body 6, and prism 8 increases spreading of light emitted from light guide body 6.